Margin Rail 1.0.4

Scrolling now batches updates once per animation frame and skips unnecessary reading-section measurements. Workspace changes reuse existing rails; slider changes update immediately with debounced, ordered settings saves.

Custom styles now apply in popout windows and are scoped to the rail and label. Cleanup removes the owned positioning class, cancels pending scroll work, and flushes pending settings on unload.

Validation: all automated checks pass, including new regression coverage for scroll bursts, 5,000 reading sections, mode changes, late indexing, multi-window styles, settings persistence, and cleanup. Native UI performance and popout behavior have not been manually re-tested in this release.